Development of lead-free Cu2BiI5 rudorffite thin films for visible light photodetector application

Abstract

Recently bismuth-based perovskites have gained intense research interest in the scenario of developing lead-free perovskites for optoelectronic applications. In the current work, we report a new rudorffite material, namely Cu2BiI5 as a successful lead replacement material. Cu2BiI5 thin films were fabricated via thermal evaporation of copper onto spin coated BiI3 thin films. Structure and morphology analysis revealed that the films formed were hexagonal Cu2BiI5 with compact surface morphologies. Raman spectra for Cu2BiI5 films showed distinct peaks at 44, 52, 83, and 112 cm−1 are reported for the first time. The films formed at the best condition showed nearly stoichiometric composition. Cu2BiI5 displayed direct bandgap values ranging from 1.53 to 1.74 eV suggest the potential absorption of light in the Vis-NIR region. Photodetector devices were fabricated using the Cu2BiI5 thin films and their visible light sensing was evaluated. The devices displayed stability and reproducibility towards different wavelengths of incident radiation, at a low bias of 0.2 V. The present investigation on the properties of Cu2BiI5 thin films suggests that it is a potential lead-replacement candidate for photodetector applications and solar energy harvesting.